Searching for Superspreaders

Whalen Dillon

May 7, 2015

Emerging Infectious Diseases

New in a population, or new but rapidly increasing

Disease Triangle

Sudden Oak Death Disease Triangle

Sudden Oak Death Hosts & Environment

46 wildland host species - 5 key host tree species

Pathogen Spillover

“when disease epidemics are driven by transmission from an alternate reservoir host population”

– Power & Mitchell (2004) Pathogen spillover in disease epidemics

A common characteristic of multihost disease systems

Superspreaders

Individual(s) that disproportionately contribute to disease transmission

– potential mechanism for pathogen spillover

Number of bay stems in the study alive during at least one sampling year: 2993

Searching for superspreaders

The 90%, 95%, and 99% quantile threshold values for each year
year slc90 slc95 slc99
1 2003 66.20 78.00 140.20
2 2004 82.00 114.00 178.00
3 2005 62.00 87.00 127.00
4 2006 112.00 130.00 174.00
5 2007 71.00 86.00 113.00
6 2008 62.00 76.00 109.81
7 2009 65.00 83.00 119.17
8 2010 103.00 138.50 191.00
9 2011 166.00 190.00 214.04
10 2012 126.00 155.00 199.75
11 2014 93.00 128.00 181.00

Searching for superspreaders

Searching for Superspreaders - Stems in the 99th Percentile

Number of observations in 99th percentiles: 272

Number of unique stems in 99th percentiles: 217

Stems in the 99th Percentile 2+ Years

d <- subset(slc99q, duplicated(slc99q$tag) | duplicated(slc99q$tag, fromLast = T))
d <- arrange(d, tag, year)
d
## Source: local data frame [97 x 5]
## 
##       plot  tag year       date slc
## 1    ANN24 1418 2007 2007-04-12 114
## 2    ANN24 1418 2011 2011-04-26 218
## 3    SDC03 1842 2008 2008-04-19 128
## 4    SDC03 1842 2014 2014-04-16 196
## 5  REDDE01  189 2008 2008-05-03 140
## 6  REDDE01  189 2012 2012-05-22 227
## 7   JLSP03 2100 2004 2004-05-19 273
## 8   JLSP03 2100 2005 2005-04-14 189
## 9   JLSP03 2100 2007 2007-05-19 114
## 10  JLSP03 2100 2010 2010-05-05 205
## ..     ...  ...  ...        ... ...

Stems in the 99th Percentile 2+ Years

Number of unique stems in the 99th percentile 2+ years: 42

Stems in the 99th Percentile 3+ Years

Number of unique stems in the 99th percentile 3+ years: 9

Species and Locations as Superspreaders

More symptoms due to:

Disease hotspots as “superspreaders”